This application relates to radio frequency (RF) and microwave devices and photonic devices.
Various applications require filtering of spectral components in signals by selecting one or more spectral components while rejecting other components. One example is bandpass filtering where a selected one or more spectral components within a spectral band are selected to transmit and spectral components outside the spectral band are rejected. A filter may be tunable, e.g., under a control of a tuning control signal, to change the frequency range of the filtered signal. As an example, a radio receiver has a tunable filter to select a desired radio station broadcast signal from many radio broadcast signals at different frequencies in the air. A television tuner is another example of such tunable filters. Many RF and microwave tunable filters are made of electronic RF and microwave circuit components.